How do you choose between DHCP failover modes: hot standby or load balance?

1 Hot standby mode

In hot standby mode, one server is the primary and the other is the secondary. The primary server handles all the DHCP requests and leases, while the secondary server only acts as a backup. The primary server periodically replicates its database to the secondary server, so that the secondary server can take over if the primary server fails. The advantage of this mode is that it provides a simple and reliable failover mechanism, but the disadvantage is that it underutilizes the resources of the secondary server.

3 Factors to consider

When deciding between hot standby and load balance modes, there are several factors to consider. For example, if you have a large or dispersed scope with many clients, load balance mode may be more efficient than hot standby mode. Additionally, if you have a low-bandwidth or high-latency connection between the servers, load balance mode could cause more traffic and delays. Furthermore, if you have servers with different hardware or software specifications, load balance mode may cause compatibility or performance issues. Finally, if you have a strict service level agreement or a high-availability requirement, load balance mode may offer more redundancy and reliability than hot standby mode.

4 How to configure DHCP failover

To configure DHCP failover, you need to have two DHCP servers running Windows Server 2012 or later, and both servers must have access to the same scope. You can use the DHCP console or PowerShell to create a failover relationship between the servers, and specify the mode, load balance percentage, state switchover interval, and other settings. You can also monitor and manage the failover status and statistics using the DHCP console or PowerShell.

5 How to test DHCP failover

Testing DHCP failover can be done through various methods, such as simulating a server failure by stopping the DHCP service or disconnecting the network cable on one server, simulating a network failure by blocking or filtering the traffic between the servers, and simulating a client failure by changing the IP configuration or releasing the IP address on a client. By doing these tests, you can check if the other server can handle DHCP requests and leases, if the servers can detect and resolve communication problems, and if the client can obtain a new IP address from either server.

6 Best practices for DHCP failover

In order to ensure a smooth and successful DHCP failover, it is important to plan and design your DHCP scope and failover settings carefully. It is also essential to use consistent hardware and software configurations for both servers, as well as keeping them updated and patched. Additionally, secure and reliable network connections between the servers should be used in order to avoid any network congestion or interference. Lastly, monitoring and troubleshooting your DHCP failover regularly is necessary in order to resolve any issues or errors promptly.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?